A relativistic dissipative hydrodynamic description for systems including particle number changing processes

TL;DR

This paper extends relativistic dissipative hydrodynamics to include particle number changing processes in a gluon system, showing their impact on temperature and spectra, and comparing hydrodynamic results with transport simulations.

Contribution

It introduces a hydrodynamic framework incorporating particle number changing processes with a rate equation based on Boltzmann and Grad's ansatz, highlighting limitations at high viscosity.

Findings

Particle production affects temperature and spectra.

Hydrodynamic results align with transport at low viscosity.

Rate equation accuracy decreases at high shear viscosity.

Abstract

Relativistic dissipative hydrodynamic equations are extended by taking into account particle number changing processes in a gluon system, which expands in one dimension boost-invariantly. Chemical equilibration is treated by a rate equation for the particle number density based on Boltzmann equation and Grad's ansatz for the off-equilibrium particle phase space distribution. We find that not only the particle production, but also the temperature and the momentum spectra of the gluon system, obtained from the hydrodynamic calculations, are sensitive to the rates of particle number changing processes. Comparisons of the hydrodynamic calculations with the transport ones employing the parton cascade BAMPS show the inaccuracy of the rate equation at large shear viscosity to entropy density ratio. To improve the rate equation, the Grad's ansatz has to be modified beyond the second moments in momentum.